Ce:LuPO4 (Ce:LOP) is a rare earth orthophosphate (REOP) crystal, whose intense emission, short fluorescent lifetime, and high positron absorption cross section could lead to more cost effective positron emission tomography (PET) instruments. It is estimated that 400 Ce:LOP crystals can replace the 12,000 BGO crystals typically used today in a PET scanner. While small research crystals can he obtained routinely by cooling a lead-based flux, large crystals suitable for incorporation into PET instruments are not readily grown. However, by introducing a proprietary, environmentally benign solvent to replace the lead-based flux, we believe high temperature solution (HTS) growth could be the key to commercial production of large Ce:LOP crystals. The temperature/composition range for phase stability of Ce:LOP will he investigated as part of the Phase I research program in order to define a robust production technology. Since the new solvent system can be applied to the growth of all REOP crystals, some of which have application as ultraviolet, visible, and infrared lasers, a commercial source of REOP crystals could ultimately lead to other new or improved medical instruments. PROPOSED COMMERCIAL APPLICATIONS: Ce:LOP scintillator crystals can he utilized for the development of compact PET instruments due to a fortuitous combination of high density, high light yield, and fast decay time. A growth process developed for Ce:LOP would apply broadly to all REOP crystals that have potential application as ultraviolet, visible, and infrared lasers, as well as polarizers and optical isolators in laser systems.